The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. In the course of integrated circuit evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased.
Various active or passive electronic components can be formed on a semiconductor IC. For example, a transformer may be formed as a passive electronic component. As device sizes continue to decrease for even higher frequency applications, traditional transformer structures may encounter problems, such as reduced mutual inductive coefficient K and reduced self-resonant frequency. Particularly, when a transformer is applied with an electrical voltage having a high frequency up to 30 GHz, the mutual inductive coefficient drops to 0.6 or less. The self-resonant frequency also drops down with decreased device size by advancing technology nodes.
Therefore, while existing transformer devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.